Ubuntu docker container running a tiny cloud-init systemd service

This image provides a simple way of faking a cloud-init systemd service. I've developped that mainly for quickly validating shell scripts sent as user-data to cloud-init services.

As this is running systemd, it can be used to develop/check systemd services interactions and dependencies when hacking your deployment scripts (but it only supports Ubuntu 16.04 Xenial packages as this is the base distro).

How to use it

With this image, it is currently required to start the container using privileged mode to make systemd work.

If you want to be able to properly shutdown the container with docker stop, you will need to define a specific stop signal (SIGRTMIN+3).

The user-data shell script file must be mounted in /var/lib/cloud/user-data. To inject environment variables, you'll need to map it to /etc/cloud-init.env.

This repository provides sample files to demonstrate that.

docker run \
	-it \
	--privileged \
	--stop-signal=SIGRTMIN+3 \
	--volume ${PWD}/sample.user-data:/var/lib/cloud/user-data:ro \
	--volume ${PWD}/sample.env:/etc/cloud-init.env:ro \
	lionelnicolas/tiny-cloud-init \

SSH service

A SSH server is installed (and enabled) in this image. If you want to be able to log into the container using SSH, you'll need to map your SSH public key file in /var/lib/cloud/ssh.pub.

You just need to add this to your docker run command:

--volume ${HOME}/.ssh/authorized_keys:/var/lib/cloud/ssh.pub:ro

Limits

This only support user-data shell scripts.

Other cloud-init services such as apt repositories or packages installation, hostname configuration, YAML-based cloud-init user-data files, or even metadata servers (169.254.169.254) are not supported.

Build

In order to build this container image instead of using the one on the Docker Hub, you can use the following command from the root directory of this repository:

docker build -t lionelnicolas/tiny-cloud-init .

License

This is licensed under the Apache License, Version 2.0. Please see LICENSE for the full license text.

Copyright 2016-2017 Lionel Nicolas